1. Field of the invention.
The present invention generally relates to terminal blocks for use in terminal connector heads, and, more particularly, to an adaptive terminal block and body capable of being mounted within connector heads of various types.
2. Description of the related art.
Terminal connector heads are commonly used with temperature sensors to serve as a device for interconnecting the sensor leads to input terminals of a control processor. A temperature sensor typically includes a temperature sensing elements such as a thermocouple, which is encased in a protective tube. The sensing element supplies or varies an electrical signal to provide an indication of the temperature level within a monitored environment. The electrical signal needs to be transmitted to a process instrument for suitable translation into usable information available for analysis. Such a process instrument might be a digital processor in combination with an analog-to-digital converter.
Terminal connector heads find particular use with temperature sensors because these sensing devices typically have short wires, preventing their direct connection to a remote facility. Terminal blocks provided in the form of an RTD-type transmitter are mounted within the terminal connector heads and interconnect the thermocouple to the process instrumentation. Standard connector heads includes a housing and a cover, in which the housing is provided with a process opening and an instrument opening. The protection tube or sheath of material surrounding a temperature sensing element is typically threaded at one end and threadably inserted into a nut adaptor formed at the process opening of the housing. The relevant wires of the sensing element are connected to the appropriate input terminals of the terminal block mounted within the housing. Connecting wires attached to the output terminals of the terminal block are routed through the instrument opening of the housing and suitably connected to the control and analysis equipment currently in use. During operation when the sensor is obtaining the relevant measurements, the interior compartment of the housing is sealed from adverse environmental conditions using the cover and by appropriately designing the terminal connector head and terminal block to withstand the expected conditions. For example, the terminal block may be formed of a high temperature ceramic while the connector head may be formed of a durable metal housing tailored to absorb significant impacts.
Industry use of terminal connector heads features two distinct types of transmitter housing heads. The DIN style commonly found in European applications employs a mounting surface for the terminal block characterized by a substantially circular design on the order of 33 mm hole diameters. By comparison, the U.S. style used in domestic applications involves an oval-shaped housing providing a substantially elliptical mounting surface for the terminal block. The consequence of such disparate and incompatible mounting arrangements has meant that conventional systems are required to provide one terminal block having circular dimensions to fit within the DIN style housing head and another terminal block having oval dimensions to fit within the U.S. style housing head. This duplication of what is essentially the same component (except for the shape of the mounting surface) has heretofore been the prevailing condition within the relevant application fields, representing a diseconomy affecting the cost of the overall system and constituting an inefficient use of parts.